U.S. patent application number 15/786127 was filed with the patent office on 2018-04-19 for method for depositing a hts on a tape, with a source reservoir, a guide structure and a target reservoir rotating about a common axis.
The applicant listed for this patent is Bruker HTS GmbH. Invention is credited to Alexander Usoskin.
Application Number | 20180108824 15/786127 |
Document ID | / |
Family ID | 57233291 |
Filed Date | 2018-04-19 |
United States Patent
Application |
20180108824 |
Kind Code |
A1 |
Usoskin; Alexander |
April 19, 2018 |
METHOD FOR DEPOSITING A HTS ON A TAPE, WITH A SOURCE RESERVOIR, A
GUIDE STRUCTURE AND A TARGET RESERVOIR ROTATING ABOUT A COMMON
AXIS
Abstract
A method for depositing a high temperature superconductor (=HTS)
onto a tape (2), in particular by pulsed laser deposition (=PLD).
The tape is wound off a source reservoir (3), heated and
transported through a deposition zone (21), and wound up at a
target reservoir (5). HTS material (32) is deposited onto the
heated transported tape in the deposition zone, and the tape is led
through the deposition zone by a guide structure (4). During
deposition of the HTS material, the source reservoir, the guide
structure and the target reservoir are rotated around a common
rotation axis (9), such that parts of the tape rotating along with
the guide structure repeatedly cross the deposition zone. This
permits depositing a HTS onto a tape, in particular by PLD, which
allows a high quality of the deposited HTS material for long tape
lengths.
Inventors: |
Usoskin; Alexander; (Hanau,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bruker HTS GmbH |
Hanau |
|
DE |
|
|
Family ID: |
57233291 |
Appl. No.: |
15/786127 |
Filed: |
October 17, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 16/408 20130101;
C23C 16/545 20130101; H01L 39/2441 20130101; H01L 39/2448
20130101 |
International
Class: |
H01L 39/24 20060101
H01L039/24; C23C 16/54 20060101 C23C016/54; C23C 16/40 20060101
C23C016/40 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 17, 2016 |
EP |
16194119.0 |
Claims
1. Method for depositing a high temperature superconductor (HTS)
onto a tape, comprising: winding the tape off a source reservoir,
heating and transporting the tape through a deposition zone, and
winding the tape up at a target reservoir, wherein HTS material is
deposited onto the heated transported tape in the deposition zone,
and wherein the tape is led through the deposition zone with a
guide structure, wherein, during the deposition of the HTS
material, the source reservoir, the guide structure and the target
reservoir are rotated around a common rotation axis such that parts
of the tape rotating along with the guide structure repeatedly
cross the deposition zone.
2. Method according to claim 1, wherein the tape is led by the
guide structure in a plurality of elongated windings, with long
sides of the elongated windings extending at least substantially in
parallel with the rotation axis.
3. Method according to claim 2, wherein for at least one long side
of each elongated winding, a normal of a flat front side of the
tape is oriented radially outward with respect to the rotation
axis, and wherein, over an entirety of the elongated windings, the
tape is led circumferentially around the rotation axis.
4. Method according to claim 3, wherein, over an entirety of the
elongated windings, the tape is led circumferentially around the
rotation axis once.
5. Method according to claim 2, wherein the elongated windings are
mutually interpenetrated, and wherein, for both long sides of each
elongated winding, the normal of the flat front side of the tape is
oriented radially outward with respect to the rotation axis.
6. Method according to claim 2, wherein the source reservoir, the
guide structure and the target reservoir rotate synchronically
about the rotation axis during the deposition.
7. Method according to claim 6, wherein a winding axis of the
source reservoir and a winding axis of the target reservoir are
oriented perpendicular to the rotation axis.
8. Method according to claim 1, wherein the guide structure
comprises a tubular system on which the tape is wound up and wound
off during the deposition, wherein the tubular system moves along
the rotation axis during the deposition caused by the winding of
the tape, and wherein, during the deposition, the tubular system is
rotated about the rotation axis in addition to the rotation caused
by winding of the tape.
9. Method according to claim 8, wherein the tubular system
comprises several tubular elements which are successively inserted
into and ejected from the guide structure during the
deposition.
10. Method according to claim 8, wherein a winding axis of the
source reservoir and a winding axis of the target reservoir are
coaxial with the rotation axis, and wherein the source reservoir,
the target reservoir and the guiding structure are rotated about
the common rotation axis with a common basic speed, overlain by
specific extra speeds caused by the winding of the tape.
11. Method according to claim 1, wherein during the deposition, the
guide structure rotates between 1 turns per second and 8 turns per
second.
12. Method according to claim 1, wherein during the deposition, the
tape rotates along with the guide structure with a circumferential
speed of between 0.3 m/s and 2.0 m/s.
13. Method according to claim 1, wherein during the deposition, the
tape is transported from the source reservoir to the target
reservoir with a linear speed of between 3 m/h and 200 m/h.
14. Method according to claim 1, wherein the tape is transported
from the source reservoir to the target reservoir under a tension
of between 5 N/mm.sup.2 and 120 N/mm.sup.2.
15. An apparatus for depositing a high temperature superconductor
(HTS) onto a tape, comprising a) a source reservoir for the tape,
b) a deposition device configured to provide HTS material (32) on
the tape in a deposition zone, c) a guide structure configured to
lead the tape through the deposition zone, d) a target reservoir
for the tape, e) a drive system configured to wind the tape off the
source reservoir, transport the tape through the deposition zone
and wind up the tape at the target reservoir, and f) a heating
device configured to heat the tape transported through the
deposition zone, wherein the source reservoir, the guide structure
and the target reservoir are mounted rotatably about a common
rotation axis, and wherein the drive system is further configured
to rotate the source reservoir, the guide structure and the target
reservoir about the common rotation axis.
16. Apparatus according to claim 15, wherein the guide structure
comprises an elongated holder extending along the rotation axis,
with a plurality of first deflectors for the tape at a first side
of the elongated holder, and a plurality of second deflectors for
the tape at a second side of the elongated holder, with the
deposition zone located between the first side and the second side,
wherein subsequent first deflectors are arranged turned against
each other about the rotation axis by a fixed offset angle, wherein
subsequent second deflectors are arranged turned against each other
about the rotation axis by the fixed offset angle, and wherein the
second deflectors are arranged turned about the rotation axis with
respect to the first deflectors by half the offset angle.
17. Apparatus according to claim 16, wherein the first and second
deflectors each comprise a roller, with each roller having a
diameter larger than a diameter of the elongated holder and with
each roller having a respective roller axis that intersects the
rotation axis at a right angle, and wherein the first deflectors
are arranged in a first axial row on the elongated holder, and the
second deflectors are arranged in a second axial row on the
elongated holder.
18. Apparatus according to claim 17, wherein pairs of the first and
the second deflectors have identical axial distances each.
19. Apparatus according to claim 16, wherein the source reservoir
and the target reservoir are mounted on the elongated holder.
20. Apparatus according to claim 15, wherein the guide structure
comprises a tubular system that comprises several separate tubular
elements and is configured to wind the tape, and is mounted
slidably along the rotation axis relative to the source reservoir
and the target reservoir.
21. Apparatus according to claim 15, further comprising a
tensioning mechanism configured to maintain a tension in the tape
during the winding.
22. Apparatus according to claim 15, wherein the heating device
comprises a tubular heater arranged coaxially with the rotation
axis, and wherein the tubular heater comprises a deposition window
through which the HTS material provided by the deposition device
accesses the deposition zone.
23. Apparatus according to claim 22, wherein the tubular heater is
surrounded by a heater screen rotatable about the rotation axis.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims foreign priority under 35 U.S.C.
.sctn.119(a)-(d) to European Application No. 16194119.0 filed on
Oct. 17, 2016, the entire contents of which are hereby incorporated
by reference.
FIELD OF INVENTION
[0002] The invention relates to a method for depositing a high
temperature superconductor (=HTS) onto a tape, in particular by
pulsed laser deposition (=PLD).
[0003] wherein the tape is wound off a source reservoir, heated and
transported through a deposition zone, and wound up at a target
reservoir,
[0004] wherein HTS material is deposited onto the heated
transported tape in the deposition zone, and wherein the tape is
led through the deposition zone by a guide structure.
[0005] Such a method is known from US 2007/0148329 A1.
BACKGROUND
[0006] High temperature superconductors (HTS) are typically used in
tape form, from which e.g. magnet coils can be wound. The tape
comprises a substrate, typically of a thin metal such as stainless
steel, coated with a layer of the HTS material; for this reason,
such tapes are also referred to as coated conductors. In general,
one or a plurality of buffer layers are arranged between the
substrate surface and the HTS layer, and often one or a plurality
of cover layers are arranged on top of the HTS layer.
[0007] A common method for depositing HTS material on a substrate
is pulsed laser deposition (PLD). In this process, short laser
pulses are shot onto a target of the HTS material to be deposited,
generating a plasma of said material. Opposing the target there is
the tape, onto which said material is then deposited. It should be
noted that for a typical tape, each spot on the tape has to be
subject to several deposition pulses, with each deposition pulse
affecting only a tiny portion of a tape, so a very large number of
deposition pulses is necessary.
[0008] It has been found that the quality of the deposited HTS
material may be improved by heating the substrate, and further
moving the tape relative to the target with a moderate speed.
Moving the tape distributes the deposition pulse over some length
of the tape. In order allow several deposition pulses on the same
spot of the tape, each tape section has to be presented numerous
times to the target.
[0009] EP 1 104 033 B1 describes a method for preparing a
superconducting layer on a tape by means of pulsed laser
deposition, wherein the tape is helically wound on a tube, with the
tube being rotated about its axis and linearly moved along its axis
during deposition.
[0010] This method allows to move the tape with respect to the
target at a desired speed by setting the rotation speed of the
tube, and thus allows a good superconductor material quality.
However, the tape length is limited by the length of the tube onto
which the tape is wound, and the required winding of tape on the
tube beforehand is cumbersome.
[0011] US 2007/0148329 A1 describes a method and an apparatus for
making a superconducting conductor, wherein a substrate tape is
wound from a rotating feed reel, led via a guide structure through
a MOCVD deposition chamber and a fed onto a rotating take-up reel.
The guide structure leads the tape on a helical path using eight
rod-like rollers.
[0012] With this method, the tape to be processed is stored on
reels, so relatively long tape lengths are possible. However, for
establishing a relative desired speed of the tape with respect to a
deposition zone, the tape would have to be wound off and up and led
through the guide structure accordingly during deposition, which
puts considerable load and abrasion on the tape. In order to
present the tape several times to the deposition zone, the tape
would have to be translated back and forth, going along with
further load and abrasion, deteriorating the overall quality of the
coated conductor.
SUMMARY
[0013] It is therefore an object of the invention to present a
method for depositing a HTS onto a tape, in particular by PLD,
allowing a high quality of the deposited HTS material for long tape
lengths.
[0014] This object is achieved, in accordance with the invention,
by a method as mentioned in the beginning, characterized in that
during deposition of the HTS material, the source reservoir, the
guide structure and the target reservoir are rotated around a
common rotation axis, such that parts of the tape rotating along
with the guide structure repeatedly cross the deposition zone.
[0015] In accordance with the invention, a desired relative speed
between the tape and a deposition zone, and in particular a
deposition device or target providing material in the deposition
zone, can be established by rotating the guide structure that leads
the tape relative to the deposition zone. The deposition zone is
basically stationary. At the same time, the source reservoir and
the target reservoir also rotate about the same rotation axis, so a
continuous feeding of the tape through the guide structure is
possible without fatal twisting of the tape. This feeding can, in
general, be done at a speed independent of the speed of rotation
about the rotation axis, in particular in a way mechanically gentle
to the tape.
[0016] In the simplest case, the source reservoir, the guide
structure and the target reservoir rotate fully synchronically
about the rotation axis (with the same speed). However note that
the rotation of the source reservoir and/or the target reservoir
and/or the guide structure about the rotation axis may be overlaid
by winding the tape off or up. So for example if the winding axes
of the source reservoir and the target reservoir are coaxial with
the rotation axis, the respective speed of rotation about the
rotation axis of the source reservoir, the guide structure and the
target reservoir may be different from each other.
[0017] By rotating the guide structure or the tape, respectively,
relative to the deposition zone, it is also possible to maintain a
desired tape temperature at a high precision. In particular, a
"quasi-equilibrium" tape heating may be established, typically
using a tubular heater configuration.
[0018] In the inventive method, there are in general two movements
of the tape: A rotational movement around the rotation axis,
basically to establish the desired tape speed with respect to the
deposition zone, and a "linear" (or feeding) movement, in general
substantially parallel to the rotation axis, basically to do the
rewinding of the tape. Note that in general, the tape coating of
the HTS material can be done in the course of a single
rewinding.
[0019] In a preferred variant of the inventive method, the tape is
led by the guide structure in a plurality of elongated windings,
with the long sides of the elongated windings extending basically
in parallel with the rotation axis. Through the plurality of
windings, a corresponding plurality of tape sections can be
presented to the deposition zone by rotating the guide structure in
quick succession. This allows a particularly fast and thermally
uniform deposition process. The basically parallel orientation
allows a simple construction, in particular with few twist of tape.
Typically, an angle between the long sides and the direction of the
rotation axis is 15.degree. or less, typically 10.degree. or
less.
[0020] A preferred further development of this variant provides
that for at least one long side of each elongated winding, a normal
of a flat front side of the tape is oriented radially outward with
respect to the rotation axis, and that over the entirety of the
elongated windings, the tape is led circumferentially around the
rotation axis, in particular once. In other words, over the
entirety of the elongated windings, the tape circumferentially
surrounds the rotation axis. This makes efficient use of the
available space. The flat front side (which is to be coated, also
called the interface side) is well accessible by the deposition
process.
[0021] In a particularly preferred further development, the
elongated windings are mutually interpenetrated, and for both long
sides of each elongated winding, the normal of the flat front side
of the tape is oriented radially outward with respect to the
rotation axis. Here the tape can be accessed at two locations per
rotation at each elongated winding, using the available space very
efficiently with a minimum of deflections necessary. Note that the
rotation axis extends basically at the center of the elongated
windings here.
[0022] In another further development, the source reservoir, the
guide structure and the target reservoir rotate synchronically
about the rotation axis during deposition, in particular wherein a
winding axis of the source reservoir and a winding axis of the
target reservoir are oriented perpendicular to the rotation axis.
This is particularly simple, with the rotation and the rewinding
being completely independent from each other. If the winding axes
are perpendicular to the rotation axis, twisting of the tape may be
reduced to a minimum, in particular if elongated windings basically
parallel to the rotation axis are used. It is also possible to have
the winding axes of the source reservoir and the target reservoir
oriented with the same angle with respect to the rotation axis. In
particular, the source reservoir and the target reservoir may also
be oriented in parallel and coaxial with the rotation axis. This
has other advantages in case of a very long tape, e.g. volume and
length (in axial direction) of side parts of a processing vacuum
chamber may be significantly smaller.
[0023] Another preferred variant provides that the guide structure
comprises a tubular system on which the tape is wound up and wound
off during deposition, said tubular system moving along the
rotation axis during deposition caused by the winding of the tape,
and that during deposition, the tubular system is rotated about the
rotation axis in addition to the rotation caused by winding of the
tape. This variant allows a support of the tape on the tubular
system during deposition, allowing good control over the tape
orientation even at high rotation speeds. Note that in general, the
linear speed of tape relative to the cylinder (tubular system) is
smaller than the rotational speed. The tubular system typically has
a circular outer cross-section.
[0024] In a preferred further development of this variant, the
tubular system comprises several tubular elements which are
successively inserted into and ejected from the guide structure
during deposition. This allows the handling of a practically
endless tape length. Note that the tubular elements act as
intermediate rollers (or roller elements) for the tape.
[0025] Another further development provides that a winding axis of
the source reservoir and a winding axis of the target reservoir are
coaxial with the rotation axis, and that the source reservoir, the
target reservoir and the guiding structure are rotated about the
common rotation axis with a common basic speed, overlain by
specific extra speeds caused by the winding of the tape. This
allows a simplified mounting of the source reservoir and target
reservoir.
[0026] In a preferred variant, during deposition, the speed of
rotation of the guide structure is between 1 turns per second and 8
turns per second. This has shown good results in practice for
typical guide structure dimensions. At such speeds, bulging of the
tape is not yet relevant.
[0027] Further preferred is a variant wherein during deposition,
the circumferential speed of the tape rotating along with the guide
structure is between 0.3 m/s and 2.0 m/s. This is fast enough to
improve the quality of the HTS coating in PLD, but bulging of the
tape is not yet relevant. Note that for guide structures with low
diameter (such as 5 cm or less), also higher circumferential speeds
such as up to 4 m/s may be acceptable.
[0028] In an advantageous variant, during deposition, the tape is
transported from the source reservoir to the target reservoir with
a linear speed between 3 m/h (approx. 8.3*10.sup.-4 m/s) and 200
m/h (approx. 5.6*10.sup.-2 m/s). This is both mechanically gentle
and allows a useful coating progress. Note that for particularly
high numbers of windings of tape on the guide structure accessible
via a rotation by the deposition zone, such as 12 or more windings,
the linear speed may be even higher, such as up to 300 m/h (approx.
8.3*10.sup.-2 m/s).
[0029] Further preferred is a variant wherein the tape is
transported from the source reservoir to the target reservoir under
a tension of between 5 N/mm.sup.2 and 120 N/mm.sup.2. Through the
tension, improved control over the tape orientation during
deposition may be achieved. In particular, bulging may be
reduced.
[0030] Also within the scope of the present invention is an
apparatus for depositing a high temperature superconductor (=HTS)
onto a tape, in particular for use in an inventive method as
described above, comprising
[0031] a) a source reservoir for the tape, in particular a source
coil,
[0032] b) a deposition device for providing HTS material on the
tape in a deposition zone,
[0033] c) a guide structure for leading the tape through the
deposition zone,
[0034] d) a target reservoir for the tape, in particular a target
coil,
[0035] e) a drive system, capable of winding the tape off the
source reservoir, transporting the tape through the deposition zone
and winding up the tape at the target reservoir, in particular via
a first drive,
[0036] f) a heating device for heating the tape transported through
the deposition zone, characterized in that the source reservoir,
the guide structure and the target reservoir are mounted rotatably
about a common rotation axis, and that the drive system is further
capable of rotating the source reservoir, the guide structure and
the target reservoir about the common rotation axis, in particular
via a second drive.
[0037] The inventive apparatus renders it possible to store the
tape in source and target reservoirs, allowing long tape lengths to
be processed by rewinding, and at the same time allow high relative
speeds of the tape with respect to a deposition zone (and e.g. a
corresponding PLD equipment) without increasing mechanical load or
abrasion by rotation. The drive system comprises at least one
motor; for example the drive system may comprise common motor for a
first drive (doing the rewinding) and a second drive (doing the
superimposed rotation), or it may comprise a plurality of
motors.
[0038] A preferred embodiment of the inventive apparatus provides
that the guide structure comprises an elongated holder extending
along the rotation axis, in particular a tube, with a plurality of
first deflectors for the tape at a first side of the elongated
holder, in particular close to the source reservoir, and a
plurality of second deflectors for the tape at a second side of the
elongated holder, in particular close to the target reservoir, with
the deposition zone being located between said first and second
sides,
[0039] that subsequent first deflectors are arranged turned against
each other about the rotation axis by a fixed offset angle,
[0040] that subsequent second deflectors are arranged turned
against each other about the rotation axis by the fixed offset
angle,
[0041] and that the second deflectors are arranged turned about the
rotation axis with respect to the first deflectors by half the
offset angle. With this embodiment, a plurality of elongated
windings of the tape can be mounted compactly, wherein the
elongated windings or the corresponding flat front sides of the
tape, respectively, can be presented to the deposition zone in
quick succession by rotating the elongated holder about the
rotation axis. From a first deflector to a respective next second
deflector, only a small angle (i.e. half an offset angle) of twist
is established, what is mechanically gentle to the tape. There are
typically at least three elongated windings. The elongated holder
may be rotated about the rotation axis by the drive system, in
particular its second drive.
[0042] A further development of the above embodiment is
characterized in that the first and second deflectors comprise a
roller each, with the roller having a diameter larger than a
diameter of the elongated holder and with a roller axis of the
roller cutting the rotation axis at a right angle, and that the
first deflectors are arranged in a first axial row on the elongated
holder, and the second deflectors are arranged in a second axial
row on the elongated holder, in particular such that pairs of first
and second deflectors have identical axial distances each. In this
arrangement, the rollers may guide the tape over two opposing sides
of the elongated holder, so each elongated winding provides the
tape two times to the deposition zone per rotation. The identical
axial distances provide for identical relaxation times between
coating sequences of the tape upon its "linear" progression
(rewinding).
[0043] In another preferred further development, the source
reservoir and the target reservoir are mounted on the elongated
holder, in particular wherein winding axes of the source reservoir
and of the target reservoir are perpendicular to the rotation axis.
Mounting the source and target reservoir on the elongated holder is
particularly simple in construction, and allows a maximum of
independency of the rotational movement of the elongated holder on
the one hand and the rewinding (linear) movement of the tape on the
other hand. With the winding axes of the source and target
reservoir being perpendicular to the rotation axis minimizes tape
twisting if the elongated windings are basically in parallel with
the rotation axis. Note that it is also possible to have the
winding axes of the source reservoir and the target reservoir
oriented with the same angle with respect to the rotation axis.
[0044] Preferred is an embodiment of the inventive apparatus
wherein the guide structure comprises a tubular system for winding
the tape, mounted slidably along the rotation axis relative to the
source reservoir and target reservoir, and comprising several
separate tubular elements. In this arrangement, the tubular system
may support the tape during rewinding, what improves the control
over the tape orientation during the HTS material deposition. The
separate tube elements can be expelled and refed in order to allow
a practically endless rewinding. Typically, the winding axes of the
source reservoir and the target reservoir are coaxial with the
rotation axis, and the tubular system or the tube elements,
respectively, are moveable through the source reservoir and the
target reservoir.
[0045] In a preferred embodiment, the apparatus comprises a
tensioning mechanism for maintaining a tension in the tape during
winding, in particular wherein the tensioning mechanism comprises a
sliding clutch with clutch discs coupled via one or a plurality of
springs. With the tensioning mechanism, bulging of the tape during
rotation can be minimized. A sliding clutch is proven in practice
and simple in construction.
[0046] In another advantageous embodiment, the heating device
comprises a tubular heater arranged coaxially with the rotation
axis, and the tubular heater comprises a deposition window for
accessing the deposition zone by the HTS material provided by the
deposition device. The tubular heater allows a uniform, quasi
equilibrium heating of the tape. The tubular heater is (at least
partially) arranged around the deposition zone.
[0047] Further preferred is a further development of the above
embodiment wherein the tubular heater is surrounded by a heater
screen rotatable about the rotation axis, in particular wherein the
heater screen has a helical form. With the heater screen, the
deposition window can at least partially be shut, improving
insulation and thus allowing a more uniform heating of the tape.
The heater screen may in particular rotate in opposite direction
relative to the guide structure leading the tape. The heater screen
may be also described as cylinder or multiwall cylinder with a
helical window (slit).
[0048] Further advantages can be extracted from the description and
the enclosed drawing. The features mentioned above and below can be
used in accordance with the invention either individually or
collectively in any combination. The embodiments mentioned are not
to be understood as exhaustive enumeration but rather have
exemplary character for the description of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] The invention is shown in the drawing.
[0050] FIG. 1 shows a schematic, partial cross-sectional side view
of an inventive apparatus for depositing a HTS on a tape, in a
first embodiment with rollers on an elongated holder;
[0051] FIG. 2 shows a schematic, partial cross-sectional top view
of a detail of the apparatus of FIG. 1, including a deposition
device and a heating device;
[0052] FIG. 3 shows a schematic perspective view of the heater
screen of FIG. 3;
[0053] FIG. 4A shows a schematic axial projection of first
deflectors of the elongated holder of FIG. 1;
[0054] FIG. 4B shows a schematic axial projection of second
deflectors of the elongated holder of FIG. 1;
[0055] FIG. 5 shows a schematic axial view of a deflection system
for use in a variant of the apparatus of FIG. 1;
[0056] FIG. 6 shows schematic, perspective view of an inventive
apparatus for depositing a HTS on a tape, in a second embodiment
with coaxial source and target reservoirs and guide structure;
[0057] FIG. 7 a mechanical coupler for use in an inventive
apparatus.
DETAILED DESCRIPTION
[0058] FIG. 1 shows s first embodiment of an inventive apparatus 1,
for performing an inventive method of depositing HTS material on a
tape 2.
[0059] The tape 2 is wound off a source reservoir 3, here a pancake
type source coil, guided via a guide structure 4 to a target coil
5, here a pancake type target coil, where the tape is wound up. The
guide structure 4 is formed by an elongated holder 6, which is here
generally tube shaped, and which also supports the source and
target reservoir 3, 5. The elongated holder 6, including the source
reservoir 3, the guide structure 4 and the target reservoir 5, can
be rotated about a rotation axis 9; the elongated holder 6 is here
supported by ball bearings 26. By this rotation, different parts of
the tape 2 are subsequently presented at a deposition zone 21,
where HTS material is coated onto the tape 2.
[0060] The elongated holder 6 supports here four first deflectors
(first deflection devices) 7a-7d, here rollers, in an axial row
near the source reservoir 3, and here another four second
deflectors (second deflection devices) 8a-8d, here again rollers,
in an axial row near the target reservoir 5. The rollers can be
rotated about a respective roller axis (see e.g. roller axis 10 at
second deflector 8b), which is perpendicular to the rotation axis 9
and intersects the rotation axis 9. Further, the rollers have a
diameter slightly larger than the elongated holder 6 here, so they
protrude beyond the elongated holder 6 on two sides (see e.g. at
second deflector 8d, at the top and at the bottom). Therefore, the
rollers or deflectors 7b-7d and 8a-8c, respectively, can be used to
give the tape 2 an approx. 180.degree. turn, and the tape 2 can be
led over the surface of the elongated holder 6 on two opposing
sides.
[0061] In more detail, the tape 2 is led from the source reservoir
3 to the first deflector 7a, then led to second deflector 8a, then
(covered in FIG. 1, on the backside of the guide structure 4) led
to first deflector 7b, then led to second deflector 8b, then
(covered in FIG. 1 again) led to first deflector 7c, then led to
the second deflector 8c, then (covered in FIG. 1 again) led to
first deflector 7d, and then led to second deflector 8d, and
finally led to the target reservoir 5. Accordingly, the tape 2 on
the guide structure 4 is led in here 31/2 elongated windings
through the deflectors 7a-7d, 8a-8d, with the elongated windings
being (with their long sides) basically in parallel with the
rotation axis 9. The tape 2 is presented with flat front sides 19
radially outward with respect to the rotation axis 9 in the area of
the elongated windings, compare e.g. normal N on the flat front
side 19 of the lowest tape section on the guide structure 4.
Subsequent first and second deflectors 7a-7d, 8a-8d, i.e. the pairs
7a /8a, 7b /8b, 7c/8c and 7d /8d, have an equal axial distance
along the rotation axis 9.
[0062] The first deflectors 7a-7d are twisted with respect to
respective next first deflectors 7a-7d in the sequence of tape
guiding by an offset angle .alpha. of here 45.degree., see also the
axial view FIG. 4A. Correspondingly, the second deflectors 8a-8d
are twisted with respect to respective next second deflectors in
the sequence of tape guiding by the same offset angle .alpha. of
here 45.degree., see also FIG. 4B. However, the subsequent first
and second deflectors 7a-7d, 8a-8d in the sequence, e.g. the first
deflector 7a and the second deflector 8a, are twisted with respect
to each other by half the offset angle .alpha./2, i.e. 22,5.degree.
here. From FIGS. 4A, 4B (and FIG. 1) it can be seen that the
elongated windings of the tape interpenetrate each other. Over all
elongated windings, the rotation axis 9 is surrounded here exactly
once. Generally speaking, the course of the tape 2 resembles a
polar helix with axially displaced return loops.
[0063] Turing to FIG. 1 again, the apparatus 1 comprises a first
drive 11, which drives the target reservoir 5 which is held in the
elongated holder 6. The target reservoir 5 has a winding axis 12
perpendicular to the rotation axis 9, and is here coupled to the
first drive 11 via a shaft 13 and bevel wheels 14, 15. By pulling
slowly via the target reservoir 5, tape 2 can be wound off the
source reservoir 3 (which can rotate about a winding axis 17
perpendicular to the rotation axis 9) and fed through the guide
structure 4 or its deflectors 7a-7d, 8a-8d, respectively. This
causes a "linear" (or feeding) movement 23 of the tape 2. At the
source reservoir 3, there is installed a tensioning mechanism 16,
here a sliding clutch/mechanical coupler coupling the source
reservoir 3 and the elongated holder 6, which keeps the tape 2 at a
minimum tension needed to compensate for a centrifugal force caused
by rotation about the rotation axis 9. The sliding clutch comprises
sliding discs coupled via one or a plurality of springs, and only
when the tension is above a limit value, a rotation corresponding
to a tooth's progress is released, with the tension not being fully
released, but kept at a minimum value, as set by said spring(s)
(not shown in FIG. 1).
[0064] Further, a second drive 18 is provided through which the
entire elongated holder 4, including the source reservoir 3, the
guide structure 4 and the target reservoir 5, can be rotated about
the rotation axis 9. By rotating the guide structure 4 together
with the tape 2, the elongated windings of the tape 2 or its
outwardly presented flat sides 19 (compare e.g. radially outward
directed normal N at the lowest tape section) pass subsequently a
deposition window 20 defining the deposition zone 21 of the
apparatus 1. Accordingly, the tape 2 undergoes a rotational
movement 22. While the "linear" movement 23 is typically rather
slow, such as about 10.sup.-1 m/s, the rotational movement 22 is
rather fast, such as 1 m/s at the tape surface.
[0065] The first drive 11 and the second drive 18 are part of a
drive system 24 of the apparatus 1, here comprising separate motors
at the first and second drive 11, 18. Note that alternatively, both
drives 11, 18 may use a common motor, with the elongated holder 6
and the target reservoir 5 being driven via different coupling and
gear systems. Further note that it is also possible to drive both
the source and target reservoir 3, 5 directly.
[0066] FIG. 2 illustrates the deposition process, here based on PLD
(pulsed laser deposition) in some more detail.
[0067] The tape 2 guided on the guide structure 4 or elongated
holder 6, respectively, is heated by a heating device 30, here
comprising a tubular heater 31. The tubular heater 31 brings the
tape 2 in its interior to a temperature of about 500.degree. C. or
even more. The tubular heater 31 exhibits the deposition window 19,
i.e. an opening through which plasma type HTS material 32 can pass.
The plasma type HTS material 32 is generated by a laser beam 33
generated by a laser 34, and here directed by a rotatable mirror 35
onto a target 36, basically made of the HTS material to be
deposited. The laser 34, the rotatable mirror 35 and the target 36
form a deposition device 39 here. It should be noted that at least
the target 36 and the tape 2 on the guide structure 4 are located
in an evacuated deposition chamber, and often practically the whole
apparatus 1 (see FIG. 1) is under vacuum conditions (note that
laser 34 may well be located under normal pressure, with the laser
beam 33 being led by a glass fiber into the deposition chamber,
though).
[0068] The heating device 30 here also comprises a heater screen
37, also of generally tubular shape, which can be rotated about the
rotation axis 9 by a motor (not shown), compare rotational movement
25.
[0069] The heater screen 37 possesses a helical slit 38, see FIG.
3, through which the HTS material 32 may pass. The heater screen 37
reduces loss of heat from the tubular heater 31 and through the
deposition window 19, and thus makes the heat distribution inside
more uniform, improving the quality of a HTS coating on the tape
2.
[0070] The pulses of the laser beam 33 (including their position on
the target 36, controlled by the position of the rotatable mirror
35) and the rotational position of the slit 38 are synchronized in
order to achieve a desired coating of the tape 2. Note that
preferably, the rotation movement 22 of the guide structure 4 and
the rotation movement 25 of the heater screen are opposite to each
other.
[0071] In FIG. 1, the winding axes 17, 12 of the source and target
reservoir 3, 5 are perpendicular to the rotation axis 9, and
oriented in parallel or close to the orientation of the roller axes
of the closest deflectors 7a, 8d. However, it is also possible to
support the source and target reservoirs 3, 5 in other orientations
on the elongated holder 6. For example, the winding axes 17, 12 may
be coaxial with the rotation axis 9. In this case, however, the
tape 2 has to be deflected, for example as shown in FIG. 5 (showing
a view along rotation axis 9). There, two auxiliary deflection
rollers 27, 28 are used to lead the tape 2 here from the last
second deflector 8d to the target reservoir 5. The auxiliary
deflection rollers 27, 28 are rigidly mounted at the elongated
holder 6.
[0072] Note that a typical diameter of the elongated holder 6 is
between 50 mm and 120 mm. The length of the elongated holder 6 is
typically between 80 cm and 200 cm, preferably between 100 cm and
160 cm. The tape 2 typically has a thin metal substrate, such as a
stainless steel substrate, and a typical HTS coating is YBCO.
Typical tape widths are generally between 4 mm and 25 mm,
preferably between 8 mm and 15 mm. Typical tape lengths processed
with the invention are 40 m or more, preferably 100 m or more.
[0073] FIG. 6 shows another embodiment of an inventive apparatus 1
for coating a tape 2 with HTS material, comprising a source
reservoir 3, here a pancake type source coil, a guide structure 4
formed by a tubular system 40 on which the tape 2 is wound, and a
target reservoir 5, here again a pancake type target coil. The
tubular system 40 comprises several tubular elements 41, 42, two of
which are shown in FIG. 6. Further, there are auxiliary deflection
rollers 43-46 for the tape 2. The source reservoir 3 and the target
reservoir 5 for the tape to be coated are mounted rotatably here on
the tubular system 40 (e.g. by ball bearings, not shown) about a
common rotation axis 9, and the tubular system 40, too, is mounted
rotatably about the rotation axis 9. In other words, the winding
axes 17, 12 of the source and target reservoir 3, 5 are coaxial
with the rotation axis 9. In the embodiment shown, there are also
source and target auxiliary reservoirs 3a, 5a for a support tape
(not shown) to be wound together with the tape 2, if desired, which
may be handled together with the respective source or target
reservoir 3, 5.
[0074] In the embodiment shown, a first drive 11 of a drive system
24 drives the target reservoir 5 (the coupling details not being
shown, for simplification), thus winding up tape 2 on the target
reservoir 5. By pulling on the tape 2, tape 2 is wound off the
tubular system 40 on the left side of FIG. 6, and tape 2 is wound
up on the right side of the tubular system 40. Further, tape 2 is
wound off the source reservoir 2; a tensioning mechanism (not
shown) can act e.g. on the source reservoir 3, if desired. Note
that depending on the amount of tape 2 already wound, the source
reservoir 3, the tubular system 40 and the target reservoir 5 may
exhibit somewhat different rotation speeds due to the rewinding
process.
[0075] By the winding of the tape 2 on the tubular system 40, the
tubular element 42 is propelled along the rotation axis 9 to the
left in FIG. 6. In order to have sufficient area of support upon
further rewinding of the tape 2, the next tubular element 41 is
moved in keeping with the previous tubular element 42 along the
rotation axis 9. Note that tubular elements will be expelled on the
left, see arrow 47, and further tubular elements have to be
inserted on the right side, see arrow 48, from time to time. The
speed of the "linear" movement 23 of the tape 2 by the rewinding
process is relatively slow, such as about 10.sup.-3 m/s.
[0076] In order to provide a higher relative speed of the tape 2 at
a deposition zone 21, in the embodiment shown, the entirety 49 of
the source reservoir 3, the guide structure 4 and the target
reservoir 5 can be rotated about the rotation axis 9 and relative
to the deposition zone 21 by a second drive 18 of the drive system
24 (the coupling details again not being shown, for
simplification). A basic rotation movement 22 of the entirety 49
about the rotation axis 9 is typically on the order of 1 m/s at the
tape surface. Note that in general, a constant relative speed of
the tape 2 with respect to the deposition zone 21 is used for
deposition. Further note that the contribution of the "linear"
movement 23 is generally negligible as compared to the contribution
of the rotation movement 22.
[0077] Alternatively, the drive system 24 may provide for separate
but synchronized driving and rotation of the source reservoir 3,
the auxiliary deflection rollers 43, 44, the tubular system 40, the
auxiliary deflection rollers 45, 46, and/or the target reservoir 5
(not shown in detail). Then the drive system 24 may be based on
well-synchronized (but not necessarily with identical rotation
speeds) drives and/or mechanical differentials. To provide such a
helical tape winder that is capable of continuous rotation, the
tubular system 40 should be capable of axial motion. This axial
motion has to be continuous and synchronized with the speed of the
tape winding.
[0078] A typical diameter of the tubular system 40 is between 20 cm
and 180 cm. Typical axial lengths of tubular elements 41, 42 are
between 30 cm and 150 cm. For typical tapes and coatings see
above.
[0079] FIG. 7 illustrates a sliding clutch/mechanical coupler 50
for use with the present invention, as a tensioning mechanism 16
(see e.g. in FIG. 1).
[0080] A tensioning mechanism in accordance with the invention may
be based on a simple friction between two discs. Preferably,
though, the tensioning mechanism is based on the power of
springs.
[0081] In the embodiment shown in FIG. 7 (with a cross section
along the winding axis 12 on the left, and a half transparent
cross-section perpendicular to the winding axis 12 on the right),
the sliding clutch/coupling mechanism 50 comprises two discs 51,
52, one of which is fixed at the elongated holder and one of which
is rotatable about the winding axis 12. The rotatable disc is
attached to the source reservoir (not shown). The discs 51, 52 have
a fixed axial distance with respect to each other. Disc 52 houses a
plurality of metallic balls 53 in housings 54, wherein the metallic
balls 53 are pretensioned towards an extended position by springs
55. Disc 51 comprises a plurality of openings 56, into which the
metallic balls 53 may penetrate when a respective housing 54 lies
opposite to the opening 56 (see left cross-section, top). If a
housing 54 lies opposite to a flat, closed part 57 of disc 51, the
metallic ball 53 is pushed back against the force of the spring 55
(see left cross-section, bottom).
[0082] As a consequence, discs 51, 52 may lock in a plurality of
relative rotational positions, depending on the number of housings
54 and the number of openings 56 distributed in the discs 52, 51.
In the example shown, disc 51 comprises nine openings 56, and disc
52 comprises ten housings 54. When pulling strong enough on the
tape wound on the source reservoir which is connected to the
rotatable disc, the disc may switch from its locked position to a
next one, whereupon some of the pulling tension is released. The
remaining pulling tension, which is not strong enough to cause
another switching of the locked position, may keep the tape
straight.
[0083] So in summary, the sliding clutch/coupling mechanics 50
shown is based on an elastic force created by a multitude of
metallic balls 53 in one disc 52, one of which enters (at least
partly) into one of a plurality of openings 56 foreseen in the
opposite disc 51.
[0084] The invention may be used to manufacture superconducting
tapes and wires, in particular HTS coated conductors. More
specifically, the invention may be used in manufacturing of cables,
particularly Roebel cables, diamagnetic screens, fault current
limiters, superconducting spools, windings, motor/generator coils,
magnets, transformers, cables, and current leads.
LIST OF REFERENCE SIGNS
[0085] 1 apparatus [0086] 2 tape [0087] 3 source reservoir [0088]
3a source auxiliary reservoir [0089] 4 guide structure [0090] 5
target reservoir [0091] 5a target auxiliary reservoir [0092] 6
elongated holder [0093] 7a-7d first deflector [0094] 8a-8d second
deflector [0095] 9 rotation axis [0096] 10 roller axis [0097] 11
first drive [0098] 12 winding axis [0099] 13 shaft [0100] 14, 15
bevel wheels [0101] 16 tensioning mechanism [0102] 17 winding axis
[0103] 18 second drive [0104] 19 flat front side [0105] 20
deposition window [0106] 21 deposition zone [0107] 22rotation
movement (guide structure) [0108] 23 linear (feeding) movement
[0109] 24 drive system [0110] 25 rotation movement (heater screen)
[0111] 26 ball bearing [0112] 27, 28 auxiliary deflection rollers
[0113] 30 heating device [0114] 31 tubular heater [0115] 32 (plasma
type) HTS material [0116] 33 laser beam [0117] 34 laser [0118] 35
rotatable mirror [0119] 36 target [0120] 37 heater screen [0121] 38
helical slit [0122] 39 deposition device [0123] 40 tubular system
[0124] 41, 42 tubular elements [0125] 43-46 auxiliary deflection
roller [0126] 47 arrow (direction of expelling tubular element)
[0127] 48 arrow (direction of inserting tubular element) [0128] 49
entirety [0129] 50 sliding clutch/mechanical coupler [0130] 51, 52
discs [0131] 53 metallic ball [0132] 54 housing [0133] 55 spring
[0134] 56 opening [0135] 57 flat, closed part [0136] .alpha. offset
angle
* * * * *